Medical balloon catheter

ABSTRACT

The medical balloon catheter of the present invention comprises a catheter shaft composed of a distal end shaft and a proximal end shaft and a balloon on the distal end of the distal end shaft, wherein the proximal end shaft is composed of a single member and the distal end portion of the proximal end shaft is lower in rigidity than the other parts thereof. The present invention also provides a medical balloon catheter having a structure in which a tube for passing a guidewire inside thereof is arranged so as to pass inside the balloon and the balloon and tube are fused together in the vicinity of the distal end of the catheter, wherein the ratio of the outer diameter of the small-diameter portion on the distal end side of the tube to the outer diameter of the proximal end portion is no less than 0.85.

TECHNICAL FIELD

The present invention relates to a medical balloon catheter used formedical applications, and more particularly to a medical ballooncatheter for percutaneous angioplasty (PTA: Percutaneous TransluminalAngioplasty, PTCA Percutaneous Transluminal Coronary Angioplasty, andthe like) during realization of peripheral angioplasty, coronaryangioplasty, valvular angioplasty, and the like.

BACKGROUND ART

Percutaneous angioplasty using medical balloon catheters has been widelyused for dilation therapy of stenoses or blocked portions of vascularcavities and for restoration or improvement of blood flow in coronaryartery, peripheral blood vessels, and the like. In a typical medicalballoon catheter, a balloon that can be inflated or contracted byinternal pressure adjustment is joined to the distal end portion of acatheter shaft, and an inner cavity (guidewire lumen) for passing aguidewire and an inner cavity (inflation lumen) for supplying a pressurefluid for internal pressure adjustment in the balloon are provided inthe longitudinal direction of the catheter shaft inside thereof.

A typical example of PTCA technique using such a medical ballooncatheter is described below. First, a guide catheter is inserted fromthe punctured zone into a large femoral artery, brachial artery,scapular artery, and the like, and the distal end thereof is disposed inthe inlet of a coronary artery via the main artery. The guidewireinserted into the guidewire lumen is then advanced through the stenoticzone, and medical balloon catheter is inserted along the guidewire, andpositioned in the stenosis. A pressure fluid is then supplied to theballoon via the inflation lumen by using an indeflator or the like, anddilatotherapy of the stenosis is conducted by inflating the balloon.After the dilatotherapy of the stenosis, PTCA is completed bycontracting the balloon by pressure reduction and pulling it out of thebody. In the present example of technique, usage of the medical ballooncatheter for PTCA in coronary artery stenosis was described, but themedical balloon catheters have been also widely employed fordilatotherapy in body cavities and other vascular cavities such asperipheral vascular cavities.

Such a medical balloon catheter has a structure in which a balloon 2 isjoined to the distal end of a catheter shaft 1, and a hub 3 forsupplying a pressure fluid for adjusting internal pressure in theballoon is joined to the catheter shaft 1. Based on the structure ofcatheter shaft 1, the catheters can be classified into two types.

The first type is the over-the-wire type (OTW type) in which theguidewire lumen 4 is provided from the proximal end side to the distalend side of the medical balloon catheter, that is, over the entirelength of the medical balloon catheter and a guidewire port is providedin the hub 3 (FIG. 1). The second type is the rapid exchange type (RXtype) in which the guidewire lumen is provided on the distal end side ofthe medical balloon catheter, and the guidewire port 5 is provided inthe middle part of catheter shaft 1 (FIG. 2).

A variety of characteristics are required from medical ballooncatheters. The main among them can be generally classified into thefollowing three groups: the ability to pass through the stenotic zone(crossability), the ability to follow the curved blood vessel(trackability), and the ability to transmit a force when the medicalballoon catheter is inserted into a blood vessel (pushability). Kinkresistance is an example of a characteristic relating to pushability.

Reducing the profile (thickness) of catheter shaft improvescrossability, but tends to degrade pushability and kink resistance.Further, increasing rigidity of catheter shaft improves pushability andkink resistance, but tends to degrade crossability. In other words, allthe above-mentioned characteristics are closely related to each other,and it is not easy to improve all the characteristics at the same time.Accordingly, a variety of techniques for improving crossability,pushability and trackability and increasing kink resistance have beendisclosed.

Examined Japanese Patent Application No. 5-28634 (Catheter) discloses arapid exchange medical balloon catheter, in which an opening of theguidewire lumen is provided in the joining region of a medium portion(distal end shaft in accordance with the present invention) and a baseportion (proximal end shaft in accordance with the present invention)and when the guidewire is contained in the guidewire lumen, the catheterreceives a continuous longitudinal support over the entire lengththereof.

Such prior art technology makes it possible to increase kink resistancein a state in which the guidewire is contained in the catheter, that is,inside the guide catheter. The drawback of that technology was that whenthe guidewire was inserted, the catheter could be easily bent in thejoining region of the medium portion and base portion and operationability by the operator was very poor.

Japanese Patent No. 2933389 (Balloon Catheter Comprising Inner Cavityfor Guidewire on the Distal End Side) discloses a medical ballooncatheter in which a transition portion extending from the distal endside of the opening of the proximal end inner cavity of the guidewirelumen to the vicinity of the distal end of the first shaft portion(proximal end shaft in accordance with the present invention) has arigidity between that of the first shaft portion and second shaftportion (distal end shaft in accordance with the present invention).

This prior art technology provides a catheter shaft with increased kinkresistance, but this increase in kink resistance is implemented byadditionally providing the second shaft with a coil-like member as adeformation preventing structure. The problem associated with suchadditional coil-like member was that the number of operations duringcatheter manufacture was greatly increased and, at the same time, theassembly method was made difficult which resulted in the increasedproduction cost. Further, with this prior art technology, thedeformation preventing structure was mounted on the outer or inner sideof the outer sleeve, or on the outer side of a core tube. When thedeformation preventing structure was mounted on the outer side of theouter sleeve, the increase in the outer diameter of the outer sleevecould degrade crossability, and when the deformation preventingstructure was mounted on the inner side of the outer sleeve or on theouter side of the cure tube, the inflation lumen was locally narrowed,producing an adverse effect on dilation or contraction behavior of theballoon.

Further, Japanese Patent Publication No. 6-507105 (Vascular CatheterComprising Guidewire Proximal End Cavity and Intermediate Member”discloses a vascular catheter comprising a main shaft (proximal endshaft in accordance with the present invention), a balloon, a plasticshaft portion (distal end shaft in accordance with the presentinvention) located between the main shaft and the balloon, anintermediate member mounted on the main shaft, extending inside theplastic shaft portion in the distal end direction and having a rigiditynot higher than that of the main shaft portion, and a guidewire lumen,wherein the guidewire inlet is withdrawn from the distal end of the mainshaft portion in the proximal end direction.

Such prior art technology provides a vascular catheter with improvedpushability and trackability and also increased kink resistance.However, kink resistance demonstrated when the vascular catheter isinserted into the guide catheter along the guidewire can hardly beconsidered good. In order to further increase kink resistance, it isnecessary to enlarge the diameter of the core wire used as a non-rigidintermediate member. However, in order to ensure the effective inflationlumen, the increase in the profile of the catheter shaft is required,and the decrease in crossability and trackability causes concerns.

Examined Japanese Patent Application No. 4-44553 (Catheter Equipped withBalloon) discloses a catheter equipped with a balloon comprising arigidity increasing member which extends in the axial direction in theouter tube and provides it with rigidity and a portion comprising nosuch rigidity increasing member at the distal end of he outer tube.

On the other hand, a balloon catheter is used to conduct dilatotherapymainly by inserting the catheter into the body passage which is theobject of therapy and introducing the internal pressure into the therapyzone. Therefore, the required mechanical properties include a strengthsufficient to prevent rupture of the balloon when a pressure necessaryfor the dilation is introduced and a capability to control the balloonsafely to the desired dilation size. Furthermore, in most cases, inorder to conduct therapy in a vascular system, the catheter has to beinserted to the zone of pathology changes and prescribed position alongthe blood vessel and the operation ability of the distal end portion ofthe catheter for such an insertion is very important.

The catheter is typically composed of thin tubular members and has to bepassed through the curved zones inside the body or narrow stenotic zonesby operating the catheter from outside of the body through the insertionopening into the body. Accordingly, a small size of the catheter itself,in particular, of the distal end thereof is very important. In addition,a force applied to the catheter from outside of the body has to beeffectively transmitted to the distal end portion and flexibility isrequired to adapt to the cured portions. Further, because guidewire isusually used by being passed inside the catheter, a small frictionresistance between the catheter and guidewire is also an importantproperty allowing for smooth movement of the catheter without disruptingthe force transmission. In order to obtain such an operation ability,the structure of a typical balloon catheter is required to have thefollowing properties: (1) flexibility of the distal end (far end)portion allowing the catheter to follow the curved internal passages,(2) strength of the proximal end (near end) portion sufficient toprovide for good transmission of force to the distal end, and (3) lowfriction and high sliding ability of the tube used for passing aguidewire in order to suppress friction resistance. Catheters satisfyingthose requirements are most often made of polyethylene, high-strengthpolyamide, or high-strength polyamide elastomers.

With respect to thinness and flexibility, a small size and flexibilityof the balloon portion at the distal end of the catheter and in thevicinity thereof are the especially important properties. Furthermore,because this portion is often inserted into the curved portions orslides over the softest portion of the guidewire inserted therein, theabsence of discontinuity in this flexibility is also required. Thus,when the catheter is disposed in a curved portion, if the flexibility isdiscontinuous, bending of the catheter becomes discontinuous, andguidewire resistance in this portion greatly increases causingdegradation of operation ability.

Further, a fixed portion of the tube for passing the balloon andguidewire is typically present as the distalmost portion “tip” at the deof balloon catheter. When this tip portion is hard, the difference inflexibility with the guidewire let out of the tip increases andguidewire can be easily bent in this zone, becoming a serious cause ofoperation ability degradation. Furthermore, in case of zone ofpathological changes with advanced calcification, the following effectsare of frequent occurrence. Thus, when an attempt is made to pass aballoon catheter along the guidewire that has been passed through such azone, if the distal end is not sufficiently thin, it is obstructed bythe hard zone of pathological changes and is not able to passtherethrough, or if the tip portion is hard, it is caught by the hardzone of pathological changes and is not able to pass therethrough.

Furthermore, in recent years, metallic stationary dilators typicallycalled stents are often used in vascular dilation therapy. In order toconduct shape dilation after stent dilation (post-dilation) and also incase of re-stenosis inside the stents and stenosis at the distal endside of the stents, the balloon catheter has to be passed inside thestents. However, in such a case, similarly to the zones of pathologicalchanges with advanced calcification, the problem was that if the distalend was not sufficiently small and the tip portion was hard, thecatheter was caught by the metallic stent and could not passtherethrough.

DISCLOSURE OF THE INVENTION

With the prior art technology described in the aforesaid openpublications, kink resistance was increased by using an outer tube withgood trackability that had a member increasing rigidity thereof.However, when the outer tube itself has a high kink resistance, or whena high kink resistance is provided with a reinforcing member such as ametal wire and the like disposed inside the outer tube, the rigidity ofthe outer tube is locally increased, but the kink resistance of theentire catheter shaft is difficult to increase. Further, the problemassociated with providing an additional component, as shown in theembodiment of the prior art technology in which a wire braid wasembedded in a plastic outer tube, is that the number of productionprocess operations was increased and production cost was raised.

This first problem can be resolved by providing a medical ballooncatheter which is easy to assemble and in which the rigidity of cathetershaft is caused to change continuously in the longitudinal direction ofthe catheter shaft and pushability and kink resistance are increased,while the profile of a catheter shaft is being held to a minimum andcrossability and trackability are being maintained.

The present invention based on the results of a comprehensive studyconducted to resolve the aforesaid first problem provides a medicalballoon catheter comprising a catheter shaft composed of a distal endshaft and a proximal end shaft, a balloon on the distal end of thedistal end shaft, and a hub provided with a port for supplying pressurefluid to the balloon on the proximal end of the proximal end shaft,wherein the distal end shaft comprises a guidewire lumen and aninflation lumen for dilating the balloon on the inner surface, theproximal end shaft is composed of a simple member and at the same timecomprises the inflation lumen on the inner surface, the distal endportion of the proximal end shaft has a rigidity lower than other partsof the proximal end shaft, and the distal end shaft and the proximal endshaft are joined together outside the distal end portion of the proximalend shaft. It is preferred that part of the distal end portion of theproximal end shaft overlap the guidewire lumen and that the distal endshaft have a rigidity lower than that of the distal end portion of theproximal end shaft. Further, the rigidity of the distal end portion ofsaid proximal end shaft may gradually decrease as the distal end side ofthe proximal end shaft is being approached.

A spiral notch is preferably provided on the distal end portion of theproximal end shaft. The pitch of the spiral in the spiral notch ispreferably no more than 5 mm, more preferably, no more than 2 mm. Thepitch of the spiral may gradually increase as the distal end side of theproximal end shaft is being approached.

The width of the spiral in the spiral notch is preferably no less than0.5 mm and no more than 10 mm, more preferably, no less than 0.5 mm andno more than 5 mm. The width of said spiral may gradually decrease asthe distal end side of the proximal end shaft is being approached.

Further, the pitch of said spiral may gradually increase as the distalend side of the proximal end shaft is being approached and the width ofsaid spiral may gradually decrease as the distal end side of theproximal end shaft is being approached.

Slits may be present on the distal end portion of said proximal endshaft instead of the spiral notch, and the slits can be present alongeither the axial direction or circumferential direction of the proximalend shaft. Further, grooves may be present on the distal end portion ofsaid proximal end shaft instead of the spiral notch, and the grooves canbe present along either the axial direction or circumferential directionof the proximal end shaft. Further, in addition, holes may be present inthe proximal end shaft instead of the above-described notch, slits, andgrooves.

The length of the distal end portion of the proximal end shaft ispreferably no less than 30 mm, more preferably, no less than 50 mm.

The proximal end shaft is preferably composed of a metal tube. In thiscase, the proximal end shaft is preferably composed of stainless steel,more preferably, of stainless steel SUS316.

Further, as described hereinabove, it is important that the distal endportion of the balloon catheter, in particular, the portion from the tipportion to the balloon portion, be thin and flexible and have nosignificant different in hardness with other portions of the catheter.This is the second problem.

A method for adhesively fixing the balloon and the tube for passing aguidewire inside thereof with an adhesive and a method for fixing byfusion are used as methods for processing the tip portion. When anadhesive fixing method is used, an adhesive layer is present. Bycontrast, with the method employing fusion, the adhesion layer is notpresent. In addition, the diameter can be easily decreased by thermalprocessing during or after fusion. Therefore, the fusion method iseffective in reducing the diameter, increasing flexibility, and reducingthe discontinuity of flexibility. However, in the conventionalcatheters, polyethylene, which is a polyolefin material, in particular,high-density polyethylene with an excellent low-friction characteristicwas most often used for the tube for passing a guidewire inside thereof(guidewire tube). High-density polyethylene is a material with excellentlow-friction characteristic, but has poor fusibility and adhesivebondability with other materials and cannot be fused to any materialsother than polyolefin materials. As a result, only adhesive bondingcould be used for joining it to other materials. On the other hand, whena balloon from a polyolefin material was used, fusion could be employed.However, because a bridge to the balloon was required, the portionserving as fusion tolerance restricted a possible reduction inthickness. As a result, the fusion process, too, could not provide forreduction of diameter and increase in flexibility of the tip portion.Furthermore, because the high-density polyethylene with excellentlow-friction characteristic has poor flexibility, the usage of alow-density polyethylene, which is a comparatively flexible material,for the guidewire tube has been considered. However, such a usage waspractically impossible because friction properties and slidingproperties rapidly degraded as the flexibility increased. When ahigh-density polyethylene single-layer tube was used as the guidewiretube, the tip portion was difficult to provide with sufficiently reduceddiameter and increased flexibility.

There are commercial balloon catheters in which a two-layer tube with anouter layer from a polyamide and an inner layer of polyethylene is usedas the tube for passing the guidewire inside thereof and the balloon ismade of the polyamide with properties identical to those of thepolyamide of the outer tube. However, because the elastic modulus ofpolyamides is typically higher than that of polyethylene, the tipportion could not be provided with sufficient flexibility.

Further, there are commercial balloon catheters comprising a balloonmade of a polyamide elastomer and a guidewire tube fabricated from apolyamide elastomer with a hardness higher and melting point also higherthan those of the polyamide elastomer of the balloon. However, because amaterial harder than the balloon was disposed in the guidewire tube, thetip portion did not have sufficient flexibility.

The second problem which is to be resolved by the present invention isto provide an improved medical balloon catheter which has excellentoperation ability because the distal end portion of the distal end ofthe catheter has a sufficiently small diameter and sufficiently highflexibility and also because the discontinuity of flexibility isreduced.

Means for resolving the second problem are provided by selecteddimensions, assembly method, and arrangement of materials.

Thus, the medical balloon catheter in accordance with the presentinvention is composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theratio of the outer diameter of the small-diameter portion on the distalend side in the tube to the outer diameter of the proximal end portion,(outer diameter of the small-diameter portion on the distal endside)/(outer diameter of the proximal end portion), is no less than0.85. With such a structure, the tip portion can be adjusted to aflexible state by increasing the flexibility of the guidewire tubeitself and by using fusion, which produces no adhesive layer, as afixing method, and the above-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention is composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theShore hardness of the material constituting at least that part of thesmall-diameter portion on the distal end side in the tube which is fusedto the balloon is less than the Shore hardness of the materialconstituting the balloon. With such a structure, the tip portion can beadjusted to a flexible state by increasing the flexibility of theguidewire tube itself and by using fusion, which produces no adhesivelayer, as a fixing method, and the above-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention is composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theflexural modulus of elasticity of the material constituting at leastthat part of the small-diameter portion on the distal end side in saidtube which is fused to the balloon is less than the flexural modulus ofelasticity of the material constituting the balloon. With such astructure, the tip portion can be adjusted to a flexible state byincreasing the flexibility of the guidewire tube itself and by usingfusion, which produces no adhesive layer, as a fixing method, and theabove-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention is composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein themelting point of the material constituting at least that part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is lower than the melting point of the materialconstituting the balloon. With such a structure, the tip portion can beadjusted to a flexible state by increasing the flexibility of theguidewire tube itself and by using fusion, which produces no adhesivelayer, as a fixing method, and the above-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention is composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in the tube are fusedtogether in the vicinity of the distal end of the catheter, wherein theouter diameter of the small-diameter portion on the distal end side inthe tube is no more than 0.52 mm. With such a structure, the tip portioncan be adjusted to a flexible state by increasing the flexibility of theguidewire tube itself and by using fusion, which produces no adhesivelayer, as a fixing method, and the above-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention has a structure in which the balloon is composed of apolyester elastomer material and at least that part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is composed of a polyester elastomer material. Withsuch a structure, fusion which is used as the fixing method producing noadhesive layer is facilitated, the tip portion can be adjusted to aflexible structure with small discontinuity of flexibility, and theabove-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention has a structure in which the balloon is composed of apolyamide elastomer material and at least that part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is composed of a polyamide elastomer material. Withsuch a structure, fusion which is used as the fixing method producing noadhesive layer is facilitated, the tip portion can be adjusted to aflexible structure with small discontinuity of flexibility, and theabove-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention has a structure in which the polyester elastomer material orthe polyamide elastomer material has soft segments and hard segments ina molecule and the ratio of soft segments in the material constitutingthe balloon is less than the ratio of soft segments in the materialconstituting the tube for passing a guidewire inside thereof. With sucha structure, the flexibility of the guidewire tube itself is increased,the tip portion can be adjusted to a flexible state, and theabove-mentioned problem is resolved.

Further, with the medical balloon catheter in accordance with thepresent invention, in addition to the above-described effects inherentto the aforesaid balloon catheter, guidewire slidability can beincreased by using a structure in which the innermost surface of thetube for passing a guidewire inside thereof is composed of high-densitypolyethylene.

Further, the medical balloon catheter in accordance with the presentinvention has a structure in which the tube for passing a guidewireinside thereof has a multilayer structure consisting of no less than twolayers, the position which is to be fused is composed of a polyamideelastomer or a polyester elastomer, the innermost surface is composed ofhigh-density polyethylene, and no less than one binder layer is present,if necessary, between the portion that has been fused and the innermostsurface. With such a structure, both the excellent guidewire slidabilityand the fusibility with the guidewire tube can be provided and theabove-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention is composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein thatpart of the small-diameter portion on the distal end side in the tubewhich is fused to the balloon is composed of a polyester elastomerhaving hard segments and soft segments in a molecule and the ratio ofthe soft segments is higher than 13%. With such a structure, the tipportion can be adjusted to a flexible state by increasing theflexibility of the guidewire tube itself and by using fusion, whichproduces no adhesive layer, as a fixing method, and the above-mentionedproblem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention is composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on the distal end side smaller than that on the proximal endside and serving as a tube for passing a guidewire inside thereof isarranged so as to pass inside the balloon and the balloon and thesmall-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein thatpart of the small-diameter portion on the distal end side in the tubewhich is fused to the balloon is composed of a polyamide elastomerhaving hard segments and soft segments in a molecule and the ratio ofthe soft segments is higher than 14%. With such a structure, the tipportion can be adjusted to a flexible state by increasing theflexibility of the guidewire tube itself and by using fusion, whichproduces no adhesive layer, as a fixing method, and the above-mentionedproblem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention has a structure in which the proximal end of an X rayimpermeable ring is abutted against and fixed to the boundary portion ofthe proximal end side and the small-diameter portion on the distal endside of the tube for passing a guidewire inside thereof. With such astructure, discontinuity of flexibility in the vicinity of the ballooncan be reduced and the above-mentioned problem is resolved.

Further, the medical balloon catheter in accordance with the presentinvention has a structure in which the tube constituting the outersurface of the catheter is composed of a material that can be fused withthe balloon and is fused and arranged on the proximal end side of theballoon. With such a structure, because no adhesive layer is formed, thedistal end side of the balloon is flexible and discontinuity offlexibility can hardly occur therein. Therefore, the above-mentionedproblem is resolved. An additional advantage from the productionstandpoint is gained when the above-described structures are employed inballoon catheters of a rapid exchange type, in which the guidewire tubeis limited to a range from the distalmost end of catheter to theintermediate part of the outer tube, because the guidewire inlet portioncan be formed by fusing the outer tube with the guidewire tube, processstability is superior to that of the molding process using adhesivebonding or the like, and the diameter of this portion can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a catheter of an over-the-wiretype, among the typical balloon catheters for PTCA;

FIG. 2 is a schematic perspective view of a catheter of a rapid exchangetype, among the typical balloon catheters for PTCA;

FIG. 3 is a schematic side view illustrating a cross section of a distalend shaft with a coaxial structure in the rapid exchange catheters whichare the typical balloon catheters for PTCA;

FIG. 4 is a cross-sectional view along the A-A′ line in FIG. 3;

FIG. 5 is a schematic side view illustrating a cross section of a distalend shaft with a biaxial structure in the rapid exchange catheters whichare the typical balloon catheters for PTCA;

FIG. 6 is a cross-sectional view along the B-B′ line in FIG. 5;

FIG. 7 is a schematic side view illustrating a case where a spiral notchis present on the distal end of a proximal end shaft in the medicalballoon catheter in accordance with the present invention;

FIG. 8 is an expanded schematic side view of the spiral notch shown inFIG. 7;

FIG. 9 is a schematic side view illustrating a case where a part of thedistal end of a proximal end shaft and an inner cavity for passing aguidewire overlap in the medical balloon catheter in accordance with thepresent invention;

FIG. 10 is a schematic side view illustrating a case where slits arepresent in the axial direction on the distal end of a proximal end shaftin the medical balloon catheter in accordance with the presentinvention;

FIG. 11 is an expanded schematic side view of the slits shown in FIG.10;

FIG. 12 is a schematic side view illustrating a case where slits arepresent in the circumferential direction on the distal end of a proximalend shaft in the medical balloon catheter in accordance with the presentinvention;

FIG. 13 is an expanded schematic side view of the slits shown in FIG.12;

FIG. 14 is a schematic side view illustrating a case where grooves arepresent in the axial direction on the distal end of a proximal end shaftin the medical balloon catheter in accordance with the presentinvention;

FIG. 15 is a cross-sectional view along the C-C′ line in FIG. 14;

FIG. 16 is a schematic side view illustrating a case where grooves arepresent in the circumferential direction on the distal end of a proximalend shaft in the medical balloon catheter in accordance with the presentinvention;

FIG. 17 is a cross-sectional view along the D-D′ line in FIG. 16;

FIG. 18 is a schematic side view illustrating a case where spiralgrooves are present on the distal end of a proximal end shaft in themedical balloon catheter in accordance with the present invention;

FIG. 19 is a schematic side view illustrating a case where holes arepresent on the distal end of a proximal end shaft in the medical ballooncatheter in accordance with the present invention;

FIG. 20 is a schematic side view illustrating a case where grooves arepresent in the circumferential direction on the distal end of a proximalend shaft and a core wire is provided in the medical balloon catheter inaccordance with the present invention;

FIG. 21 is a schematic view illustrating a system for evaluating themedical balloon catheter;

FIG. 22 is an expanded view of the curved plate shown in FIG. 21;

FIG. 23 is a cross-sectional schematic view illustrating the distal endportion of the balloon catheter containing a balloon and a tip portionof the balloon catheter in accordance with the present invention;

FIG. 24 is a cross-sectional schematic view illustrating the distal endportion of the balloon catheter containing a balloon and a tip port ionof the balloon catheter in accordance with the present invention;

FIG. 25 is a cross-sectional schematic view illustrating the entirerapid exchange balloon catheter in accordance with the presentinvention;

FIG. 26 is a cross-sectional view along the E-E′ line in FIG. 23 and isa cross-sectional schematic view illustrating an example of the tipportion of the balloon catheter in accordance with the presentinvention;

FIG. 27 illustrates schematically a measurement system used forEvaluation 3 employed for demonstrating the effect of the presentinvention; and

FIG. 28 illustrates schematically a measurement system used forEvaluation 4 employed for demonstrating the effect of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Various embodiments of the medical balloon catheter in accordance withthe present invention will be described below. First, the embodimentsrelating to a catheter shaft will be explained with reference to FIGS. 2through 22.

The medical balloon catheter of the present embodiment has a structurein which, as shown in FIG. 2, a balloon 2 is joined to a distal end of acatheter shaft 1 and a hub 3 for supplying pressure fluid for adjustingthe internal pressure of the balloon is joined to the catheter shaft 1,and relates to a rapid exchange catheter in which a guidewire lumen 4 isprovided only at the distal end side of the balloon catheter and aguidewire port 5 is provided in the medium portion of catheter shaft 1.The catheter shaft 1 of the present embodiment is composed of a distalend shaft 10 and a proximal end shaft 11 which are connected to eachother in a joint zone 12. In this case, no limitation is placed on thestructure of the distal end shaft 10, on condition that the guidewirelumen 4 and an inflation lumen 6 are provided therein. In other words, acoaxial structure may be employed in which, as shown in FIG. 3 and FIG.4, an inner tube 7 and an outer tube 8 are installed so that the distalend shaft 10 has a coaxial double-wall configuration and which has theguidewire lumen 4 demarcated by the inner surface of the inner tube 7and the inflation lumen 6 demarcated by the inner surface of the outertube 8 and the outer surface of the inner tube 7, or a biaxial structuremay be employed in which, as shown in FIG. 5 and FIG. 6, the guidewirelumen 4 and inflation lumen 6 are arranged in parallel. Other structuresalso place no limitation on the effect of the present invention. Thereference symbol 9 in the figures stands for a ring impermeable to Xrays.

The proximal end shaft 11 is composed of a single member, and a specificfeature thereof is that the distal end portion 13 of the proximal endshaft 11 has a rigidity lower than that of the other parts of theproximal end shaft 11. No limitation is placed on means for reducing therigidity of the distal end portion 13 of the proximal end shaft 11, andthe rigidity of the distal end portion can be reduced by forming aspiral notch 14, slits 17, grooves 21, and holes 26. The optimumrigidity reduction means can be selected and implemented based on thetarget profile or application of the medical balloon catheter,processing cost, and the like.

No limitation is placed on the method for forming the spiral notch 14,slits 17, grooves 21, and holes 26, but from the standpoint ofprocessing accuracy, the formation method using a laser is preferred.The type of the laser to be used can be determined and selected bytaking into account the material of the proximal end shaft 11 and thelike.

When the rigidity of the distal end portion 13 of the proximal end shaft11 is reduced with a spiral notch 14, as shown in FIG. 7 and FIG. 8, apitch 15 of the spiral is preferably no more than 5 mm. The pitch 15 ofthe spiral, as referred to herein, means the width of the notch in theaxial direction of the shaft (see FIG. 8). When the pitch 15 of thespiral is greater than 5 mm, the rigidity of the proximal end shaft 11decreases abruptly in the distal end portion 13, and the increase inpushability and kink resistance, which is the object of the presentinvention, is difficult to attain.

Because the rigidity of the proximal end shaft 11 is determined by theprofile and material, the rigidity of the distal end portion 13 of theproximal end shaft can be optimized by changing the pitch 15 of thespiral according to the application of the medical balloon catheter.With consideration for the profile required for the proximal end shaft11 when the medical balloon catheter is designed for PTCA, it ispreferred that the pitch 15 of the spiral be no more than 2 mm. When therigidity is thus optimized, a portion of the distal end of proximal endshaft 11 may overlap the guidewire lumen 4.

The pitch 15 of the spiral can be gradually increased as the distal endside of the proximal end shaft 11 is being approached in order torealize a medical balloon catheter in which continuous distribution ofrigidity in the entire catheter shaft is obtained due to gradualreduction of rigidity of distal end portion 13 of the proximal end shaft11 toward the distal end of the proximal end shaft 11 and which has evenbetter kink resistance. In this case, the degree of gradual increase inthe pitch 15 of the spiral can be adjusted and optimized by taking intoaccount the rigidity of proximal end shaft 11 and distal end shaft 10.

Further, when the rigidity of the distal end portion 13 of the proximalend shaft is reduced by the above-mentioned spiral notch, it ispreferred that the width 16 of the spiral be of no less than 0.5 mm andof no more than 10 mm. The width 16 of the spiral as referred to hereinmeans the width of the portion sandwiched between the notches in theaxial direction of the shaft. When the width 16 of the spiral is lessthan 0.5 mm, the rigidity decreases abruptly in the distal end portion13 of the proximal end shaft and the kink resistant is difficult toincrease. Furthermore, when the width 16 of the spiral exceeds 10 mm,the rigidity changes at the distal end side more abruptly than in theproximal end shaft 11 and the continuous distribution of rigidity isdifficult to realize.

Because the rigidity of the proximal end shaft 11 is determined by theprofile and material, the rigidity of the distal end portion 13 of theproximal end shaft can be optimized by changing the width 16 of thespiral according to the application of the medical balloon catheter.With consideration for the profile required for the proximal end shaft11 when the medical balloon catheter is designed for PTCA, it ispreferred that the width 16 of the spiral be no less than 0.5 mm and nomore than 5 mm. When the rigidity is thus optimized, a portion of thedistal end of proximal end shaft 11 may overlap the guidewire lumen 4.

The width 16 of the spiral can be gradually decreased as the distal endside of the proximal end shaft 11 is being approached in order torealize a medical balloon catheter in which continuous distribution ofrigidity in the entire catheter shaft is obtained due to gradualreduction of the rigidity of distal end portion 13 of the proximal endshaft toward the distal end of the proximal end shaft 11 and which haseven better kink resistance. In this case, the degree of gradualdecrease in the width 16 of the spiral can be adjusted and optimized bytaking into account the rigidity of proximal end shaft 11 and distal endshaft 10. Moreover, the rigidity of distal end portion 13 of theproximal end shaft may be also optimized by gradually increasing thepitch 15 of the spiral as the distal end of the proximal end shaft 11 isbeing approached and by gradually decreasing the width 16 of the spiralas the distal end of the proximal end shaft 11 is being approached.

When the rigidity of the distal end portion 13 of the proximal end shaftis reduced with slits 17, as shown in FIGS. 10 through 13, the slits maybe present in either the axial direction or circumferential direction ofthe proximal end shaft. As shown in FIG. 10 and FIG. 11, when the slitsare present in the axial direction, a more continuous distribution ofrigidity in the entire catheter shaft can be obtained by changing thespacing 18, width 19, and length 20 of the slits. When the slits arepresent in the circumferential direction, as shown in FIG. 12 and FIG.13, the same effect can be produced by changing the spacing 18 and width19 of the slits.

Further, when the rigidity of the distal end portion 13 of the proximalend shaft is reduced with grooves 21, as shown in FIGS. 14 through 18,the grooves 21 may be present in either the axial direction (see FIGS.14 and 15) or circumferential direction (see FIGS. 16 and 17) of theproximal end shaft or may be in the form of a spiral (see FIG. 18). Amore continuous distribution of rigidity in the entire catheter shaftcan be obtained by changing the width 22, spacing 23, and length 24 ofthe grooves, in the same manner as discussed with reference to slits 17.

When the rigidity of the distal end portion 13 of the proximal end shaftis reduced with holes 26, as shown in FIG. 19, a more continuousdistribution of rigidity in the entire catheter shaft can be obtained bychanging the shape, size, and spacing of holes 26, in the same manner asdiscussed with reference to slits 17 or grooves 21.

The length of the distal end portion 13 of the proximal end shaft 11 ispreferably no less than 30 mm. When it is less than 30 mm, changes ofthe rigidity of the distal end portion 13 of the proximal end shaft 11become abrupt and sufficient kink resistance is difficult to realize. Asdescribed above, because the rigidity of the distal end shaft 11 isdetermined by the profile and material, the rigidity of the distal endportion 13 of the proximal end shaft 11 can be optimized by changing thelength of the distal end portion 13 of the proximal end shaft 11. Withconsideration for the profile required for the proximal end shaft 11when the medical balloon catheter is designed for PTCA, it is especiallypreferred that the length of the distal end portion 13 of the proximalend shaft 11 be no less than 0.5 mm and no more than 50 mm.

A specific feature of the present invention is that the distal end shaft10 and proximal end shaft 11 are joined outside the distal end portion13 of the proximal end shaft. The reference symbol 12 in the figuresdenotes the joint zone of the distal end shaft 10 and proximal end shaft11. Spiral notch 14, slits 17, grooves 21, holes 26, or the like areprovided to change continuously the rigidity of the distal end portion13 of the proximal end shaft 11. In particular, if the distal end shaft10 is joined in the distal end portion 13 of the proximal end shaft 11,when through passages are made in the wall surface of the proximal endshaft 11, as in the case of spiral notch 14, slits 17, and holes 26, aliquid-tight structure of the inflation lumen 6 of the medical ballooncatheter is difficult to obtain and the balloon cannot be caused toexpand or contract.

No limitation is placed on the method for joining the distal end shaft10 and proximal end shaft 11. In other words, well-known technology canbe used therefor. For example, adhesive bonding with an adhesive orfusion, if the distal end shaft 10 and proximal end shaft 11 arefusible, can be used. Furthermore, no limitation is placed on thecomposition, chemical structure or curing system of the adhesive usedfor joining. In other words, in terms of composition and chemicalstructure, adhesives of urethane, silicone, epoxy, cyanoacrylate, andother types can be used. In terms of curing system, adhesives oftwo-liquid mixed type, UV-curable adhesives, adhesives curable by waterabsorption, heat-curable adhesives, radiation-curable adhesives, and thelike can be used. It is preferred that the adhesive have a hardnessafter curing such that the rigidity of the joint zone 12 of the distalend shaft 10 and proximal end shaft 11 do not change discontinuously viathe adhesive bonding zone, and the adhesive can be selected by takinginto account the rigidity of the distal end shaft 10 and proximal endshaft 11.

In accordance with the present invention, the rigidity of the distal endshaft 10 is preferably lower than that of the distal end portion 13 ofthe proximal end shaft. As a result, the distribution of rigidity in thelengthwise direction of the medical balloon catheter is such that therigidity gradually decreases toward the distal end of the medicalballoon catheter and a contribution is made to the increase of kinkresistance and, at the same time, to the improvement of trackability.However, when the rigidity of the distal end shaft 10 is too low bycomparison with that of the distal end portion 13 of proximal end shaft11, though the distribution of rigidity in the lengthwise direction ofthe medical balloon catheter is a gradually decreasing one, the degreeof gradual decrease increases. As a result the kink resistance can bereduced. In such a case, as shown in FIG. 20, the rigidity can beadjusted by arranging a core wire 27 inside the distal end shaft 10. Thecore wire 27 as referred to herein means a member mounted on theproximal end shaft 11, distal end shaft 10, or hub 3 and extendinginside the distal end shaft 10 toward the distal end.

When the rigidity of the distal end shaft 10 is higher than that of thedistal end portion 13 of the proximal end shaft 11, the lowest rigidityof the catheter shaft is in the distal end portion 13 of the proximalend shaft 11 and the distribution of rigidity becomes discontinuous.Such a discontinuity not only reduces the kink resistance, but alsocauses the decrease in pushability and trackability and degrades theperformance of the medical balloon catheter as a whole.

From the standpoint of crossability, it is advantageous that the profileof the distal end shaft 10 be as small as possible, but the profile hasto be determined by taking into account the rigidity, cross sectionalarea of inflation lumen 6, cross sectional area of guidewire lumen 4,diameter of the guidewire used in the catheter, and the like. Theprofile changes depending on the usage and application of the medicalballoon catheter, but the outer diameter is 0.75-3.00 mm, preferably,0.80-2.50 mm.

Similarly, from the standpoint of crossability, it is advantageous thatthe profile of the proximal end shaft 11 be as small as possible, butthe profile has to be determined by taking into account the rigiditydistribution, cross sectional area of inflation lumen 6, and the like.The profile changes depending on the usage and application of themedical balloon catheter, but the outer diameter is 0.55-2.00 mm,preferably, 0.60-1.50 mm.

Dipping molding, blow molding, and the like are used as method for themanufacture of balloon 2 that can be inflated or contracted by internalpressure adjustment and is provided on the distal end of the distal endshaft 10, and the appropriate method can be selected according to theusage and application of the medical balloon catheter. In case ofmedical balloon catheters designed for dilatotherapy of stenoticportions of blood vessels or body cavities, blow molding is preferredbecause it provides for sufficient resistance to pressure. As anexample, first, a tubular parison of any size is molded by extrusionmolding or the like. This tubular parison is placed in a die having amold matching in shape the balloon and stretched in the axial directionand radial direction by a biaxial stretching process. To mold a balloonof the same shape as that of the die. The biaxial stretching process maybe conducted under heating or repeated several times. Furthermore, axialstretching and radial stretching may be conducted simultaneously orsequentially. Further, the balloon may be subjected to annealing tostabilize the shape and size of the balloon.

The balloon 2, as shown in FIG. 2 and FIG. 3, comprises a straighttubular portion 2 a and joining portions 2 b, 2 b for conductingliquid-tight joining at the distal end side and proximal end side of thestraight tubular portion. Tapered portions 2 c are provided between thestraight tubular portion 2 a and joining portions 2 b. The size ofballoon 2 is determined by the usage and application of the medicalballoon catheter. The outer diameter of straight tubular portion 2 a inthe balloon inflated by the internal pressure adjustment is 1.50-35.00mm, preferably 1.50-30.00, and the length of straight tubular portion 2a is 10.00-80.00 mm, preferably, 10.00-60.00 mm.

No limitation is placed on the resin material of the tubular parison.Examples of suitable materials include polyolefins, polyolefinelastomers, polyesters, polyester elastomers, polyamides, polyamideelastomers, polyurethanes, polyurethane elastomers, and the like.Blended materials prepared by blending two or more of those resinmaterials or multilayer structures obtained by lamination of two or morethereof may be also used.

No limitation is placed on the material of the proximal end shaft 11.Examples of suitable materials include polyolefins, polyolefinelastomers, polyesters, polyester elastomers, polyamides, polyamideelastomers, polyurethanes, polyurethane elastomers, polyimides,polyimidoamides, polyetherimides, polyetherketones,polyetheretherketones, metals of a variety of types, and the like.However, when a balance of continuity of rigidity distribution in theentire medical balloon catheter, pushability, trackability, and the likeis taken into account, it is preferred that a metal tube be used. Fromthe standpoint of production cost, it is more preferred that the metalbe a stainless steel tube, and with consideration for rigidity of theproximal end shaft 11 itself, it is even more preferred that stainlesssteel SUS316 be used. Further, when the above-mentioned resin materialsare used for the proximal end shaft 11, the rigidity may be adjusted byarranging a core wire 27 inside the proximal end shaft 11 or in theproximal end shaft 11 and distal end shaft 10 to provide for thecontinuity of rigidity distribution in the entire medical ballooncatheter.

No limitation is placed on the material of tubes constituting the distalend shaft 10. When the distal end shaft 10 has a coaxial structure,polyolefins, polyolefin elastomers, polyesters, polyester elastomers,polyamides, polyamide elastomers, polyurethanes, polyurethaneelastomers, and the like can be used for the inner tube 7. When thedistal end shaft has a coaxial structure, because the guidewire lumen 4is demarcated by the inner surface of the inner tube 7, from thestandpoint of guidewire slidability it is preferred that polyethylene,in particular, high-density polyethylene, be used. The inner tube 7 canalso have a multilayer structure, with the innermost layer being fromhigh-density polyethylene and the outermost layer being from a materialthat can be adhesively bonded with or fused with the balloon 2. In orderto improve further the guidewire slidability, a lubricating coating ofsilicone, Teflon, or the like can be provided on the inner surface ofinner tube 7.

No limitation is placed on the material of outer tube 8. Thus,polyolefins, polyolefin elastomers, polyesters, polyester elastomers,polyamides, polyamide elastomers, polyurethanes, polyurethaneelastomers, and the like, can be used.

Further, even when the distal end shaft 10 has a biaxial structure orany other structure, materials suitable for the above-described innertube 7 or outer tube 8 can be used.

Resins such as polycarbonates, polyamides, polyurethanes, polysulfones,polyallylates, styrene-butadiene copolymers, polyolefins, and the likecan be advantageously used as the material constituting the hub 3.

In order to improve visibility of balloon 2 under X ray imaging and tofacilitate positioning of the balloon in the target zone of pathologicalchanges, an X ray impermeable ring 9 may be provided on the outersurface of the distal end shaft present inside the balloon. The X rayimpermeable ring 9 may be of any material with X ray impermeability, andmetals or resins may be used for the ring. No limitation is also placedon the position and number of such rings and they can be set accordingto the target usage of the medical balloon catheter.

A hydrophilic coating can be provided on the outer surface of themedical balloon catheter to facilitate the insertion into blood vesselsor guide catheter. Thus, a hydrophilic coating providing lubricationduring contact with blood to zones which are in contact with blood ispreferably provided on the outer surface of distal end shaft 10, outersurface of proximal end shaft 11, outer surface of balloon 2, and thelike. No limitation is placed on the type of such hydrophilic coating,but hydrophilic polymers such as poly(2-hydroxyethyl methacrylate),polyacrylamide, polyvinyl pyrrolidone, or the like can be advantageouslyused. No limitation is placed on the coating method.

Depending on the target usage of the medical balloon catheter, ahydrophobic coating can be provided on the outer surface of balloon 2 inorder to prevent slipping in the zone of pathological changes duringinflation of balloon 2. No limitation is placed on the type of suchhydrophobic coating. Hydrophobic polymers such as silicones can beadvantageously used for the coating.

An embodiment relating to the structure of the distal end portionincluding the balloon of the medical balloon catheter in accordance withthe present invention will be explained below with reference to FIGS. 23through 28, but the present invention is not limited thereto. Thepresent invention relates to a balloon catheter composed of a pluralityof tubes. FIGS. 23 and 24 illustrate an example in which the distal endportion comprises a balloon of the balloon catheter in accordance withthe present invention, a tube having a lumen for passing a guidewire andformed so that the outer diameter on the distal end side is smaller thanthat on the proximal end side, and a tip portion.

Referring to FIG. 23, a tube 41 having a lumen for passing a guidewireis formed so that the outer diameter on the distal end portion 43 issmaller than that of the proximal end portion 42 and is arranged to passinside the balloon 44. At the distalmost end of the catheter, the tubeis coaxially fused, as shown in FIG. 26 (cross sectional view along theE-E′ line in FIG. 23) to balloon 44, forming a tip portion. The balloon44, on the other end thereof, is fused with a tube 45 constituting theouter surface of the catheter. The X ray impermeable ring 49 is designedso that the inner diameter thereof is larger than the outer diameter ofthe distal end portion 43 of tube 41 and smaller than the outer diameterof proximal end portion 42. The proximal end of X ray impermeable ring49 is abutted onto and fixed to the boundary zone between the distal endportion and a small-diameter portion on the distal end side in tube 41.Referring to FIG. 24, the tube 41 having a lumen for passing a guidewireis formed so that the outer diameter of distal end portion 43 is lessthan the outer diameter of the proximal end portion 42 and that theinner diameter of distal end portion 43 is less than the inner diameterof distal end portion 42. Furthermore, tube 41 is arranged to passinside the balloon 44, and at the distalmost end of the catheter, thetube is coaxially fused, as shown in FIG. 26 (cross sectional view alongthe E-E′ line in FIG. 23) with balloon 44, forming a tip portion. On theother hand, the proximal end of balloon 44 is fused with a tube 45constituting the outer surface of the catheter.

The inner diameter on the distal end side of tube 41 formed so that theouter diameter of distal end portion 43 is less than that of 42 may beequal to the inner diameter of proximal end portion, as shown in FIG.23, or maybe less than the inner diameter of proximal end portion, asshown in FIG. 24.

FIG. 25 is a cross-sectional schematic view illustrating the entirerapid exchange balloon catheter in accordance with the presentinvention. The rapid exchange balloon catheter as referred to herein istypically a balloon catheter with a structure in which the tube 41 forpassing a guidewire is made short in order to facilitate the exchange ofthe balloon catheter. The present invention is, however, not limited tothe rapid exchange balloon catheters.

An embodiment of the present invention will be described below ingreater detail. The present invention relates to a balloon cathetercomposed of a plurality of tubes and a balloon, this catheter having astructure in which the tube 41 formed to have an outer diameter on thedistal end side smaller than that of the proximal end side and servingas the tube 41 for passing a guidewire inside thereof is arranged so asto pass inside the balloon and the balloon 44 and the small-diameterportion on the distal end side in the tube 41 are fused together in thevicinity of the distal end of the catheter, wherein the ratio of theouter diameter of the small-diameter portion on the distal end side intube 41 to the outer diameter of the proximal end portion, (outerdiameter of small-diameter portion on the distal end side)/(outerdiameter of proximal end portion), is no less than 0.85. Because fusionis used for fixing the balloon 44 and tube 41, no adhesive layer isformed. As a result, the tip portion is provided with flexibility anddiscontinuity of flexibility therein can be reduced. Furthermore, fromthe standpoint of reducing the diameter and providing for continuity offlexibility, it is preferred that the ratio of the outer diameter of thesmall-diameter portion on the distal end side to the outer diameter ofthe proximal end portion, (outer diameter of small-diameter portion onthe distal end side)/(outer diameter of proximal side portion), be noless than 0.85 and no more than 0.95. Thus, if the ratio less than 0.85,flexibility becomes discontinuous and an adverse effect can be produced.When the ratio is above 0.95, the degree of flexibility enhancement inthe distal end of the catheter owing to diameter reduction is small. Onthe other hand, in addition to the structure shown in FIG. 23 and FIG.24 in which a step is formed between the large-diameter section and asmall-diameter section, a tapered structure with gradually changingdiameter or a structure combining those two structures can be used. Inthis case, the diameter of tube 41 in the vicinity (in the positionshifted by 5 mm from the fusion portion toward the proximal end) of thefusion portion with the distal end side of balloon 44 is used as theouter diameter of the small-diameter portion on the distal end side, anda diameter of tube 41 for passing a guidewire directly below the fusionportion (directly below the center of the fusion portion) of theproximal end side of balloon 44 and tube 45 constituting the outersurface of the catheter is used as the outer diameter of the proximalend portion. Further, from the standpoint of reducing the discontinuityof rigidity, the ratio of the thickness of the small-diameter portion onthe distal end side and the thickness of the proximal end portion ispreferably no less than 0.7, even more preferably, no less than 0.8.

Further, the present invention relates to a balloon catheter composed ofa plurality of tubes and a balloon, this catheter having a structure inwhich the tube 41 formed to have an outer diameter on the distal endside smaller than that of the proximal end side and serving as the tube41 for passing a guidewire inside thereof is arranged so as to passinside the balloon and the balloon 44 and the small-diameter portion onthe distal end side in the tube 41 are fused together in the vicinity ofthe distal end of the catheter, wherein any of the values of Shorehardness, or flexural modulus of elasticity, or melting point at leastof that part of the small-diameter portion on the distal end side in thetube 41 which is fused with the balloon 44 are less that the respectivevalues of the material constituting the balloon 44. Setting specificlimitations on Shore hardness, flexural modulus of elasticity, andmelting point makes it possible to improve further the flexibility ofthe guidewire tube itself, in addition to the effect obtained by forminga structure in which the ratio of the outer diameter of thesmall-diameter portion on the distal end side to the outer diameter ofthe portion on the proximal end side is no less than 0.85 and no morethan 0.95, and to provide a balloon catheter with a more flexible distalend.

Further, the present invention provides a balloon catheter aimed attherapy of coronary artery and composed of a plurality of tubes and aballoon, this catheter having a structure in which the tube 41 formed tohave an outer diameter on the distal end side smaller than that on theproximal end side and serving as the tube 41 for passing a guidewireinside thereof is arranged so as to pass inside the balloon 44 and theballoon 44 and the small-diameter portion on the distal end side in thetube 41 are fused together in the vicinity of the distal end of thecatheter, wherein the outer diameter of the small-diameter portion onthe distal end side in said tube is no more than 0.52 mm. As for theouter diameter of tube 41, in case of catheters for expanding a coronaryartery, the outer diameter of no more than 0.52 mm and no less than 0.49mm is preferred from the standpoint of strength required for the tube41. Thus, if the outer diameter is above 0.52 mm, the degree offlexibility provided to the distal end of catheter is small, and if itis less than 0.49, the problem is associated with the decreasedresistance of the tube to pressure.

Further, the balloon catheter in accordance with the present inventionhas a structure such that when the balloon 44 is composed of a polyesterelastomer material or a polyamide elastomer material, at least that partof the small-diameter portion on the distal end side of guidewire tube41 which is fused with the balloon 44 is formed of the resin of the sametype as the balloon 44, that is from a polyester elastomer material or apolyamide elastomer material. As a result, fusion, which produces noadhesive layer, can be conducted. Therefore, the diameter of the tipportion can be decreased, flexibility can be improved, and discontinuityof flexibility can be reduced. Furthermore, in case of a structure inwhich the above-mentioned polyester elastomer materials or polyamideelastomer materials have hard segment and soft segment components in amolecule, employing a structure in which the ratio of soft segments inthe material constituting the balloon 44 is less than the ratio of softsegments in the material constituting the tube 41 for passing aguidewire inside thereof makes it possible to provide a balloon catheterin which the flexibility of the tube 41 itself is increased and theflexibility of the distal end is increased.

No specific limitation is placed on the inner surface of guidewire tube41, and a single-layer tube 41 may be made from the same material as theportion fused with the balloon 44, provided that a minimum requiredguidewire slidability is ensured. However, because materials with a lowShore hardness, flexural modulus, and melting point typically have poorsliding properties, it is preferred that a material with excellentsliding properties, which is different from that of the portion fusedwith the balloon 44, be arranged on the inner surface, and the innermostsurface is preferably composed of high-density polyethylene.Furthermore, to enable fusion with the balloon 44, the portion of theguidewire tube 41, which is to be fused with the balloon 44, ispreferably composed of a material with excellent fusibility with theballoon 44. Moreover, when the balloon 44 is composed of a polyesterelastomer, the portion of tube 41 which is to be fused with the balloon44 is preferably composed of a polyester elastomer, and when the balloon44 is composed of a polyamide elastomer, the portion of tube 41 which isto be fused with the balloon 44 is preferably composed of a polyamideelastomer. The portion which is to be fused with balloon 44, as referredto herein, may be located anywhere, provided that it is a portionallowing the two members to be fixed by mixing with the materialconstituting the balloon during fusion and solidifying, but it isespecially preferred that this portion be the outermost layer 46 of thetube 41. With the present structure, the guidewire tube 41 can beprovided with a combination of fusion ability and high guidewireslidability. In this case, a layer of a material for providing the tube41 with described mechanical properties, or a binder layer 47 may bepresent between the innermost layer and the portion which is to be fusedwith the balloon 44, no limitation being placed on the number, type, andthickness ratio of such layers. For example, when a binder layer 47 isformed, the conventional lamination technology and adhesive bondingtechnology can be applied. A safer balloon catheter in which interfacepeeling between the portion which is to be fused with the balloon 44 andthe innermost surface 48 is made difficult can be provided if one or aplurality of materials having a solubility parameter (SP value) betweenthose of the material layers constituting the portion which is to befused with balloon 44 and the innermost surface 48 is arrangedtherebetween, or a material having adhesive properties is arranged onthe portion which is to be fused with balloon 44 and the innermostsurface. When the layer forming the portion which is to be fused withthe balloon 44 is from a thermoplastic elastomer such as a polyesterelastomer or a polyamide elastomer, it is preferred that the calculatedflexural rigidity of the elastomer layer represented by a product of thetensile modulus of the elastomer and the geometrical moment of inertiadetermined by the dimensions and shape of the elastomer layer becontrolled so as to be greater than that of the other layers. Further,as described above, the tube 41 represented in accordance with thepresent invention is often preferred to have a multilayer structure, andthe tube 41 with the entirely multilayer structure can be used, but thetube in which only the small-diameter portion on the distal end side andvicinity thereof has a multilayer structure may be also used. Referringto FIG. 26, the reference symbol 51 stands for a material layeroriginating from balloon 44; 52—material layer originating from theoutermost surface of guidewire tube 41; 53—material layer originatingfrom the binder layer of guidewire tube 41; and 54—material layeroriginating from the innermost surface of guidewire tube 41. Since FIG.26 is a cross-sectional view along the E-E′ line in FIG. 23, referencesigns 52, 53 and 54 of FIG. 26 correspond to reference signs 46, 47 and48, respectively, of FIGS. 23 and 24.

Further, the present invention provides a balloon catheter aimed attherapy of coronary artery and composed of a plurality of tubes and aballoon, this catheter having a structure in which the tube 41 formed tohave an outer diameter on the distal end side smaller than that on theproximal end side and serving as the tube 41 for passing a guidewireinside thereof is arranged so as to pass inside the balloon 44 and theballoon 44 and the small-diameter portion on the distal end side in thetube 41 are fused together in the vicinity of the distal end of thecatheter, wherein that part of the small-diameter portion on the distalend side in the tube 41 which is to be fused with the balloon 44 iscomposed of a polyester elastomer having hard segments and soft segmentsin a molecule, and the ratio of soft segments is above 13%. From thestandpoint of providing the distal end of catheter with flexibility, itis preferred that the ratio of soft segments of the polyester elastomerforming the part which is to be fused with balloon 44 be above 13%. Thetip portion can be adjusted to a flexible condition by increasingflexibility inherent to guidewire tube 41 and by using fusion, whichproduces no adhesive layer, as a fixing method. On the other hand, it ispreferred that the ratio of soft segments of the polyester elastomerforming the part which is to be fused with the balloon 44 be less than70%, in order to prevent extreme deformation in response to pressureapplied when the balloon 44 is inflated.

Further, the present invention provides a balloon catheter aimed attherapy of coronary artery and composed of a plurality of tubes and aballoon, this catheter having a structure in which the tube 41 formed tohave an outer diameter on the distal end side smaller than that on theproximal end side and serving as the tube 41 for passing a guidewireinside thereof is arranged so as to pass inside the balloon 44 and theballoon 44 and the small-diameter portion on the distal end side in thetube 41 are fused together in the vicinity of the distal end of thecatheter, wherein that part of the small-diameter portion on the distalend side in the tube 41 which is to be fused with the balloon 44 iscomposed of a polyamide elastomer having hard segments and soft segmentsin a molecule, and the ratio of soft segments is above 14%. From thestandpoint of providing the distal end of catheter with flexibility, itis preferred that the ratio of soft segments of the polyamide elastomerforming the part which is to be fused with balloon 44 be above 14%. Thetip portion can be adjusted to a flexible condition by increasingflexibility inherent to guidewire tube 41 and by using fusion, whichproduces no adhesive layer, as a fixing method. On the other hand, it ispreferred that the ratio of soft segments of the polyamide elastomerforming the part which is to be fused with the balloon 44 be less than70%, in order to prevent extreme deformation in response to pressureapplied when the balloon 44 is inflated.

In the medical balloon catheter, the X ray impermeable ring 49preferably is abutted against and fixed to the boundary portion of theproximal end side and the small-diameter portion on the distal end sideof the guidewire tube 41. Thus, if the X ray impermeable ring 49 isarranged on the proximal end side which is thicker than the distal endportion 43, the flexibility of the portion where the ring is arrangedwill be further decreased by comparison with that on the distal endside. Moreover, because the X ray impermeable ring 49 is arranged sothat it abuts against the boundary portion on the proximal end side,changes of flexibility from the thick proximal end side to the thindistal end side are smoothed and discontinuity of flexibility can bereduced.

Further, in accordance with the present invention, a structure may bealso provided in which the tube 41 constituting the outer surface of thecatheter is composed of a material fusible with the balloon 44 and fusedwith and arranged on the proximal end side of balloon 44. Employing astructure in which the tube 45 constituting the outer surface of thecatheter is fused with the proximal end side of balloon 44 makes itpossible to provide a medical balloon catheter which is flexible and inwhich discontinuity of flexibility hardly occurs on the proximal endside of balloon 44, because no new adhesive layer is formed.

Shore hardness indicated in the present invention can be measured by themethod indicated in ASTM D 2240, flexural modulus of elasticity can bemeasured by the method indicated in ASTM D 790, and tensile modulus ofelasticity can be measured by the method indicated in ASTM D 638.Melting point can be measured by using the conventional DSC measurementapparatus. The ratio of hard segments and soft segments in the materialsindicated in the present invention is a weight ratio of components inthe materials and can be measured by NMR.

EMBODIMENTS OF CATHETER SHAFT

The catheter shaft of the medical balloon catheter in accordance withthe present invention will be described below in greater detail, basedon specific embodiments and comparative examples thereof, but thepresent invention is not limited thereto.

Embodiment 1

A tubular parison (inner diameter 0.43 mm, outer diameter 0.89 mm) wasfabricated by an extrusion molding method by using a polyamide elastomer(trade name: PEBAX7233SA01, manufactured by Elf Atochem Co.). Then, aballoon with an outer diameter of a straight tube portion of 3.0 mm wasfabricated by a biaxial stretching and blowing method by using theparison.

The inner tube (inner diameter 0.42 mm, outer diameter 0.56 mm) and anouter tube (inner diameter 0.71 mm, outer diameter 0.88 mm) werefabricated by extrusion molding by using a polyamide elastomer (tradename: PEBAX7233SA01, manufactured by Elf Atochem Co.). The balloon andouter tube were joined by thermal fusion. Then, the inner tube and outertube were arranged so as to obtain a coaxial double-wall tubularconfiguration and the balloon and inner tube were joined by thermalfusion. Notches with a length of half a perimeter in the circumferentialdirection were provided in part of the outer tube, the inner tube wasthereafter fused in an exposed state to the outer surface of the outertube, and a guidewire port was formed. The product was employed as adistal end shaft—balloon assembly. The outer surface of the balloon wascoated with an aqueous solution of polyvinyl pyrrolidone.

A proximal end shaft (inner diameter 0.50 mm, outer diameter 0.66 mm)was fabricated from a stainless steel SUS316.

A spiral notch with a width of the spiral of 2 mm and a pitch of thespiral of 0.5 mm was formed by laser processing on a distal end portionwith a length of 60 mm. The proximal end shaft and the distal endshaft—balloon assembly were arranged as shown in FIG. 7 and adhesivelybonded with a two-liquid mixed-type urethane adhesive (trade nameUR0531, manufactured by H. B. Fuller Co., Ltd.).

A hub was fabricated by an injection molding method using apolycarbonate (trade name Makloron 2658, manufactured by Bayer Co.).Once the hub and proximal end shaft have been adhesively joined with atwo-liquid mixed-type urethane adhesive (trade name UR0531, manufacturedby H. B. Fuller Co., Ltd.), the balloon was subjected to lapping and EOGsterilization treatment was conducted.

Embodiment 2

Fabrication was conducted in the same manner as in Embodiment 1, exceptthat slits with a width of 0.3 mm and a spacing of 2 mm were providedwith a length of half a perimeter in the circumferential direction bylaser processing on a distal end portion (with a length of 50 mm) of aproximal end shaft, as shown in FIG. 12.

Embodiment 3

Fabrication was conducted in the same manner as in Embodiment 1, exceptthat four round holes with a diameter of 0.4 mm were produced with equalspacing on the same circumference by laser processing on a distal endportion (with a length of 40 mm) of a proximal end shaft, the distancebetween the holes in the axial direction being 0.5 mm, as shown in FIG.19.

Embodiment 4

The distal end portion of the proximal end shaft of Embodiment 1 wasstretched to obtain a width of the spiral of 2 mm and a pitch of thespiral of 1.6 mm. Upon completion of stretching, fabrication wasconducted in the same manner as in Embodiment 1, except that the distalend portion of the proximal end shaft was cut to a length of 60 mm.

Embodiment 5

Fabrication was conducted in the same manner as in Embodiment 1, exceptthat, as shown in FIG. 20, the proximal end shaft was fabricated from athermosetting polyimide, grooves with a width of 0.1 mm, a depth of 0.1mm, and a spacing of 5 mm were produced by laser processing on a distalend portion (with a length of 70 mm) of a proximal end shaft, a corewire from stainless steel SUS 314 with a diameter of 0.25 mm wasarranged from inside the proximal end shaft to the proximal end side ofdistal end shaft, and the core wire was adhesively bonded and secured tothe outer peripheral surface of inner tube with a two-liquid mixed-typeurethane adhesive (trade name UR0531, manufactured by H. B. Fuller Co.,Ltd.).

COMPARATIVE EXAMPLE 1

Fabrication was conducted in the same manner as in Embodiment 1, exceptthat no spiral notch of Embodiment 1 was provided in the distal endportion of proximal end shaft.

COMPARATIVE EXAMPLE 2

Fabrication was conducted in the same manner as in Embodiment 5, exceptthat no groove of Embodiment 5 was provided in the distal end portion ofproximal end shaft.

Embodiments 1 through 5 and Comparative Examples 1, 2 were evaluated bythe following methods.

(Evaluation 1)

As shown in FIG. 21 and FIG. 22, an aorta model 29 and a guide catheter31 were placed in a water tank 28 filled with a physiological solutionat a temperature of 37° C., and a hemostat valve 32 was secured to theguide catheter. The distal end of guide catheter 31 was connected to acurved plate 33 simulating the coronary artery, and a guidewire 30 witha diameter of 0.014″ (about 0.36 mm) was pre-inserted into the guidecatheter 31. A polyethylene tube 34 was arranged in the curved plate 33.The polyethylene tube 34 was composed of a straight portion 36 and acurved portion 35. The length of the straight portion 36 was 80 mm, thecurvature radius of the curved portion 35 was 15 mm, the outer diameter37 of the polyethylene tube 34 was 5 mm, and the inner diameter 38thereof was 3 mm. The far end of guidewire 30 was arranged at a distanceof 50 mm from the far end of curved plate 33. The operation ability wasevaluated when a medical balloon catheter was inserted from outside thewater tank via the hemostat valve along the guidewire 30 located insidethe guide catheter 31. The evaluation results are shown in Table 1.

(Evaluation 2)

Upon completion of Evaluation 1, the medical balloon catheter was pushedat a rate of 10 mm/sec to the far end portion of curved plate 33connected to the distal end of guide catheter 31 by using a slide table,and a maximum generated load was measured with a digital force gage. Theevaluation results are shown in Table 1.

Evaluation 1 was used to evaluate the kink resistance during insertionof the medical balloon catheter into a body from outside of the body.Evaluation 2 was mainly used to evaluate the trackability. Therefore,good results of both evaluations are the target effect of the presentinvention.

In Evaluation 1, good insertion operation ability was demonstrated inEmbodiments 1 through 5 and kink formation was observed in none of theportions of the catheter shaft when it was passed through the hemostatvalve.

On the other hand, in Comparative Examples 1, 2 a kink appeared in thecatheter shaft in the distalmost portion of proximal end shaft when itpassed through the hemostat valve. Kink formation could be prevented byconducting insertion at a very low speed, while grasping the distalmostportion of the proximal end shaft, but in such a case a large load wasplaced on the operator manipulating the medical balloon catheter and theoperation ability could not be considered good.

In Evaluation 2, no kink appeared during passage through an aorta arc 29a or curved plate in Embodiments 1 through 5, a maximum load value wasfrom 0.54 N to 0.71 N, and good trackability was demonstrated.

In Comparative Examples 1, 2 a kink appeared in the distalmost portionof proximal shaft when the distalmost portion of the proximal end shaftreached the vicinity of aorta arc 29 a, and the medical balloon catheterwas difficult to insert from the aorta arc to the distal end side.Therefore, trackability in Comparative Examples 1, 2 was considered tobe very poor.

TABLE 1 Measurement results on kink resistance and trackabilityEvaluation 1 Evaluation 2 Embodiment 1 Good insertion operation Maximumgenerated load ability, no kink appeared 0.65 N Embodiment 2 Goodinsertion operation Maximum generated load ability, no kink appeared0.60 N Embodiment 3 Good insertion operation Maximum generated loadability, no kink appeared 0.71 N Embodiment 4 Good insertion operationMaximum generated load ability, no kink appeared 0.54 N Embodiment 5Good insertion operation Maximum generated load ability, no kinkappeared 0.59 N Comparative Kink in the distal end Kink in thedistalmost Example 1 portion of proximal end portion of proximal endshaft shaft in aorta arc Comparative Kink in the distal end Kink in thedistalmost Example 2 portion of proximal end portion of proximal endshaft shaft in aorta arc

Embodiment of Distal End Portion of Catheter

More specific embodiments and comparative examples of the distal endportion of the medical balloon catheter in accordance with the presentinvention will be described below. The embodiments described below placeno limitation on the present invention.

Embodiment 6

A rapid exchange balloon catheter for coronary artery with a distal endportion of the catheter shown in FIG. 2 was fabricated by passing aguidewire tube, in which the layer forming the outermost surface wascomposed of a polyester elastomer with a Shore hardness of 60D, aflexural modulus of elasticity of 274 MPa, a melting point of 216° C.,and soft segment ratio of 22%, the innermost surface was composed of ahigh-density polyethylene, the outer diameter and inner diameter of thedistal end portion were 0.50 mm and 0.40 mm, respectively, and the outerdiameter and inner diameter of the proximal end portion were 0.56 mm and0.42 mm, respectively, inside a balloon with a rated expansion value of3.0 mm formed from a polyester elastomer with a Shore hardness of 72D, aflexural modulus of elasticity of 568 MPa, a melting point of 218° C.,and a soft segment ratio of 13% and coaxially fusing the outer surfaceof the tube at the distal end of the distal end side of the balloon. Theproximal end of the X ray impermeable ring was fixed in a positionabutting against the boundary portion of the proximal end side and thesmall-diameter portion on the distal end side in the tube. Further, apolyester elastomer was used for the tube constituting the outer surfaceof the catheter, and the proximal end side of the balloon and the tubeconstituting the outer surface of the catheter were joined by fusion.The maximum diameter of the tip portion was 0.57 mm and the maximumdiameter of the section from the tip portion to the balloon portion was0.77 mm in the zone where the tapered portion of the balloon was foldedin the vicinity of the boundary of the tip and balloon.

Embodiment 7

A rapid exchange balloon catheter for coronary artery with a distal endportion of the catheter shown in FIG. 24 was fabricated by passing aguidewire tube, in which the layer forming the outermost surface wascomposed of a polyamide elastomer with a Shore hardness of 55D, aflexural modulus of elasticity of 196 MPa, a melting point of 168° C.,and a soft segment ratio of 35%, the innermost surface was composed of ahigh-density polyethylene, the outer diameter and inner diameter of thedistal end portion were 0.51 mm and 0.39 mm, respectively, and the outerdiameter and inner diameter of the proximal end portion were 0.56 mm and0.42 mm, respectively, inside a balloon with a rated expansion value of3.0 mm formed from a polyamide elastomer with a Shore hardness of 70D, aflexural modulus of elasticity of 430 MPa, a melting point of 172° C.,and a soft segment ratio of 14% and coaxially fusing the outer surfaceof the tube at the distal end of the distal end side of the balloon. Theproximal end of the X ray impermeable ring was fixed in a positionabutting against the boundary portion of the proximal end side and thesmall-diameter portion on the distal end side in the tube. Further, apolyamide elastomer was used for the tube constituting the outer surfaceof the catheter, and the proximal end side of the balloon and the tubeconstituting the outer surface of the catheter were joined by fusion.The maximum diameter of the tip portion was 0.56 mm and the maximumdiameter of the section from the tip portion to the balloon portion was0.77 mm in the zone where the tapered portion of the balloon was foldedin the vicinity of the boundary of the tip and balloon.

COMPARATIVE EXAMPLE 3

A rapid exchange balloon catheter for coronary artery was fabricated bypassing a tube for passing a guidewire, in which the layer forming theoutermost surface was composed of a polyester elastomer with a Shorehardness of 60D, a flexural modulus of elasticity of 274 MPa, a meltingpoint of 216° C., and a soft segment ratio of 22%, the innermost surfacewas composed of a high-density polyethylene, and the outer diameter andinner were 0.56 mm and 0.42 mm, respectively, inside a balloon with arated expansion value of 3.0 mm formed from a polyester elastomer with aShore hardness of 72D, a flexural modulus of elasticity of 568 MPa, amelting point of 218° C., and a soft segment ratio of 13% and coaxiallyfusing the outer surface of the tube at the distal end of the distal endside of the balloon. Further, a polyester elastomer was used for thetube constituting the outer surface of the catheter, and the proximalend side of the balloon and the tube constituting the outer surface ofthe catheter were joined by fusion. The maximum diameter of the tipportion was 0.63 mm and the maximum diameter of the section from the tipportion to the balloon portion was 0.83 mm in the zone where the taperedportion of the balloon was folded in the vicinity of the boundary of thetip and balloon.

COMPARATIVE EXAMPLE 4

A rapid exchange balloon catheter for coronary artery was fabricated bypassing a tube for passing a guidewire, in which the layer forming theoutermost surface was composed of a polyamide elastomer with a Shorehardness of 55D, a flexural modulus of elasticity of 196 MPa, a meltingpoint of 168° C., and a soft segment ratio of 35%, the innermost surfacewas composed of a high-density polyethylene, and the outer diameter andinner diameter were 0.56 mm and 0.42 mm, respectively, inside a balloonwith a rated expansion value of 3.0 mm formed from a polyamide elastomerwith a Shore hardness of 70D, a flexural modulus of elasticity of 430MPa, a melting point of 172° C., and a soft segment ratio of 14% andcoaxially fusing the outer surface of the tube at the distal end of thedistal end side of the balloon. Further, a polyamide elastomer was usedfor the tube constituting the outer surface of the catheter, and theproximal end side of the balloon and the tube constituting the outersurface of the catheter were joined by fusion. The maximum diameter ofthe tip portion was 0.62 mm and the maximum diameter of the section fromthe tip portion to the balloon portion was 0.85 mm in the zone where thetapered portion of the balloon was folded in the vicinity of theboundary of the tip and balloon.

COMPARATIVE EXAMPLE 5

A rapid exchange balloon catheter for coronary artery was fabricated bypassing a tube for passing a guidewire, in which the layer forming theoutermost surface was composed of a polyester elastomer with a Shorehardness of 72D, a flexural modulus of elasticity of 568 MPa, a meltingpoint of 218° C., and a soft segment ratio of 13%, the innermost surfacewas composed of a high-density polyethylene, and the outer diameter andinner were 0.56 mm and 0.42 mm, respectively, inside a balloon with arated expansion value of 3.0 mm formed from a polyester elastomer with aShore hardness of 72D, a flexural modulus of elasticity of 568 MPa, amelting point of 218° C., and a soft segment ratio of 13% and coaxiallyfusing the outer surface of the tube at the distal end of the distal endside of the balloon. Further, a polyester elastomer was used for thetube constituting the outer surface of the catheter, and the proximalend side of the balloon and the tube constituting the outer surface ofthe catheter were joined by fusion. The maximum diameter of the tipportion was 0.63 mm and the maximum diameter of the section from the tipportion to the balloon portion was 0.85 mm in the zone where the taperedportion of the balloon was folded in the vicinity of the boundary of thetip and balloon.

COMPARATIVE EXAMPLE 6

A rapid exchange balloon catheter for coronary artery was fabricated bypassing a tube for passing a guidewire, in which the layer forming theoutermost surface was composed of a polyamide elastomer with a Shorehardness of 70D, a flexural modulus of elasticity of 430 MPa, a meltingpoint of 172° C., and a soft segment ratio of 14%, the innermost surfacewas composed of a high-density polyethylene, and the outer diameter andinner diameter were 0.56 mm and 0.42 mm, respectively, inside a balloonwith a rated expansion value of 3.0 mm formed from a polyamide elastomerwith a Shore hardness of 70D, a flexural modulus of elasticity of 430MPa, a melting point of 172° C., and a soft segment ratio of 14% andcoaxially fusing the outer surface of the tube at the distal end of thedistal end side of the balloon. Further, a polyamide elastomer was usedfor the tube constituting the outer surface of the catheter, and theproximal end side of the balloon and the tube constituting the outersurface of the catheter were joined by fusion. The maximum diameter ofthe tip portion was 0.63 mm and the maximum diameter of the section fromthe tip portion to the balloon portion was 0.85 mm in the zone where thetapered portion of the balloon was folded in the vicinity of theboundary of the tip and balloon.

COMPARATIVE EXAMPLE 7

A commercial rapid exchange balloon catheter for coronary artery with arated expansion value of 3.0 mm was used that was manufactured bypassing a tube for passing a guidewire, in which the layer forming theoutermost surface was composed of a polyamide with a melting point of178° C. and the innermost surface was composed of a high-densitypolyethylene, inside a balloon formed from a polyamide with a meltingpoint of 178° C. and coaxially fusing the outer surface of the tube atthe distal end of the distal end side of the balloon. Further, apolyamide elastomer was used for the tube constituting the outer surfaceof the catheter, and the proximal end side of the balloon and the tubeconstituting the outer surface of the catheter were joined by fusion.The maximum diameter of the tip portion was 0.78 mm and the maximumdiameter of the section from the tip portion to the balloon portion was0.89 mm in the zone where the tapered portion of the balloon was foldedin the vicinity of the boundary of the tip and balloon.

COMPARATIVE EXAMPLE 8

A commercial rapid exchange balloon catheter for coronary artery with arated expansion value of 3.0 mm was used that was manufactured bypassing a tube for passing a guidewire, which was composed of apolyamide with a melting point of 176° C. and a soft segment ratio of7%, inside a balloon formed from a polyamide with a melting point of173° C. and a soft segment ratio of 17% and coaxially fusing the outersurface of the tube at the distal end of the distal end side of theballoon. Further, a polyamide elastomer was used for the tubeconstituting the outer surface of the catheter, and the proximal endside of the balloon and the tube constituting the outer surface of thecatheter were joined by fusion. The maximum diameter of the tip portionwas 0.64 mm and the maximum diameter of the section from the tip portionto the balloon portion was 0.82 mm in the zone where the tapered portionof the balloon was folded in the vicinity of the boundary of the tip andballoon.

Characteristics of guidewire tubes and balloons of various types used inthe above-described Embodiments 3, 4 and Comparative Examples 3 through8 are presented in Table 2 and Table 3, respectively.

TABLE 2 Characteristics of tubes for passing a guidewire that were usedin embodiments and comparative examples Ratio of Shore Flexural Meltingsoft Diameter Diameter Material Material hardness of modulus of point ofsegments in of distal of proximal of of material of material materialmaterial of end side end side outer- inner- outer-most of outer- ofouter- outer-most Outer Inner Outer Inner most most layer most layermost layer layer diam., diam., diam., diam., Units layer layer — MPa °C. % mm mm mm mm GT1 TPEE HDPE 60D 274 216 22 0.50 0.40 0.56 0.42 GT2TPAE HDPE 55D 196 168 35 0.51 0.39 0.56 0.42 GT3 TPEE HDPE 60D 274 21622 0.56 0.42 0.56 0.42 GT4 TPAE HDPE 55D 196 168 35 0.56 0.42 0.56 0.42GT5 TPEE HDPE 72D 568 218 13 0.56 0.42 0.56 0.42 GT6 TPAE HDPE 70D 430172 14 0.56 0.42 0.56 0.42 GT7 PA HDPE 178 0 GT8 TPAE TPAE 176 7 Note:TPEE: polyester elastomer TPAE: polyamide elastomer PA: polyamide HDPE:high-density polyethylene

TABLE 3 Characteristics of balloons used in embodiments and comparativeexamples Rated expansion Flexural Ratio value of Shore modulus ofMelting of soft balloon hardness elasticity point segments Units mmMaterial — MPa ° C. % B1 3.0 TPEE 72D 568 218 13 B2 3.0 TPAE 70D 430 17214 B3 3.0 PA 178 0 B4 3.0 TPAE 173 17 Note: TPEE: polyester elastomerTPAE: polyamide elastomer PA: polyamide(Evaluation)

Comparison of tip portions of Embodiments 6, 7, which are the ballooncatheters in accordance with the present invention, with any of tipportions of Comparative Examples 3, 4, 5, 6, 7, and 8 demonstrates thatthe tip portions of the embodiments have a smaller maximum diameterwithin a range from the tip to the balloon portion and are moreflexible. Further, discontinuity of flexibility in Embodiments 6 and 7did not seem to be large.

The balloon catheters of Embodiments 6, 7 and Comparative Examples, 3,4, 5, 6, 7, and 8 were tested by passing a balloon catheter 55 along aguidewire 57 at a constant rate in the evaluation system (Evaluation 3)shown schematically in FIG. 27, that is, in a constricted channel 56 inthe model through which the guidewire 57 has been passed, and a loadthat was applied to the balloon catheter when the balloon passed throughthe constricted portion from the tip was measured. The inner diameter ofthe constricted portion in the constricted channel 56 inside the modelwas 0.65 mm and the channel was molded from a silicone with a Shorehardness of 40 D. The measurement was conducted in a state in which theballoon of the balloon catheter was folded on the periphery of guidewiretube.

The balloon catheters of Embodiments 6, 7 and Comparative Examples, 3,4, 5, 6, 7, and 8 were also tested by passing a balloon catheter 55along a guidewire 57 at a constant rate in the evaluation system(Evaluation 4) shown schematically in FIG. 28, that is, in a curvedchannel 60 in a model body fabricated from a polyethylene tube with aninner diameter of 1.5 mm that was curved at 90 degrees and had acurvature of 5 mm. The channel had a guidewire 57 arranged insidethereof and physiological solution with a temperature adjusted to 37.degree. C. was circulated therein. In the test, a load that was appliedto the balloon catheter 55 when the tip portion passed through thecurved portion was measured. The inner surface of the polyethylene tubeserving as the curved channel 60 inside the model body was coated with ahydrophilic coating to prevent the effect of the surface state of theballoon catheter.

The results of Evaluation 3 and Evaluation 4 are presented in Table 4.The results show that the balloon catheters of Embodiments 6, 7 inaccordance with the present invention could be passed into theconstricted channel 56 in the model body with a load lower than thatrequired in comparative example, had a small diameter of the zone fromthe tip portion to the balloon portion, and had excellent operationability. Those results also show that in the balloon catheters of theembodiments, the balloon catheter tip portions could be passed throughthe curved channel 60 in the model body with a load lower than thatrequired in comparative example, the tip portion were flexible, and thecatheters had excellent operation ability.

TABLE 4 Structures of embodiments and comparative examples and theresults obtained with measurement systems of Evaluations 3 and 4Structure of catheter distal end portion Measurement results GuidewireEvaluation 3 Evaluation 4 tube Balloon Load peak (N) Load peak (N)Embodiment 6 GT1 B1 0.355 0.085 Embodiment 7 GT2 B2 0.310 0.077Comparative GT3 B1 0.638 0.118 Example 3 Comparative GT4 B2 0.688 0.098Example 4 Comparative GT5 B1 0.690 0.333 Example 5 Comparative GT6 B20.689 0.314 Example 6 Comparative GT7 B3 1.095 0.343 Example 7Comparative GT8 B4 0.657 0.265 Example 8 Note: GT1 - 8 correspond toTable 2, B1 - 4 correspond to Table 3.

INDUSTRIAL APPLICABILITY

In accordance with the present invention, a medical balloon catheter canbe readily provided in which the rigidity of catheter shaft is caused tochange continuously in the longitudinal direction of the catheter shaftand pushability and kink resistance are increased, while the profile ofa catheter shaft is being held to a minimum and crossability andtrackability are being maintained.

Further, with the present invention, a medical balloon catheter can beobtained in which the zone from the tip to the balloon is thin, theflexibility of the tip portion is high and discontinuity of flexibilityis small, this medical balloon catheter having excellent operationability, in particular, the ability to penetrate into highly constrictedzones of pathological changes, highly curved zones of pathologicalchanges, and very hard zones of pathological changes.

1. A medical balloon catheter composed of a plurality of tubes and aballoon, this catheter having a structure in which a tube formed to havean outer diameter on a distal end side is consistently smaller along theentire length thereof than that on a proximal end side and serving as atube for passing a guidewire inside thereof is arranged so as to passinside the balloon and the balloon and the small-diameter portion on thedistal end side in said tube are fused together in the vicinity of thedistal end of the catheter, wherein a ratio of the outer diameter of thesmall-diameter portion on the distal end side in said tube to the outerdiameter of the proximal end portion, (outer diameter of thesmall-diameter portion on the distal end side)/(outer diameter of theproximal end portion), is no less than 0.85, wherein the outer diameterof the small-diameter portion on the distal end side in said tube is nomore than 0.52 mm, wherein a proximal end of an X ray impermeable ringis abutted against and permanently fixed to the boundary portion of theproximal end side and the small-diameter portion on the distal end sideof the tube for passing a guidewire inside thereof, wherein a tubeconstituting the outer surface of the catheter is composed of a materialthat can be fused with the balloon and is fused and arranged on theproximal end side of the balloon.
 2. A medical balloon catheter composedof a plurality of tubes and a balloon, this catheter having a structurein which a tube formed to have an outer diameter on a distal end side isconsistently smaller along the entire length thereof than that on aproximal end side and serving as a tube for passing a guidewire insidethereof is arranged so as to pass inside the balloon and the balloon andthe small-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein aShore hardness of the material constituting at least that part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is less than the Shore hardness of the materialconstituting the balloon, wherein a ratio of the outer diameter of thesmall-diameter portion on the distal end side in said tube to the outerdiameter of the proximal end portion, (outer diameter of thesmall-diameter portion on the distal end side)/(outer diameter of theproximal end portion), is no less than 0.85, wherein the outer diameterof the small-diameter portion on the distal end side in said tube is nomore than 0.52 mm, wherein a proximal end of an X ray impermeable ringis abutted against and permanently fixed to the boundary portion of theproximal end side and the small-diameter portion on the distal end sideof the tube for passing a guidewire inside thereof, wherein a tubeconstituting the outer surface of the catheter is composed of a materialthat can be fused with the balloon and is fused and arranged on theproximal end side of the balloon.
 3. A medical balloon catheter composedof a plurality of tubes and a balloon, this catheter having a structurein which a tube formed to have an outer diameter on a distal end side isconsistently smaller along the entire length thereof than that on aproximal end side and serving as a tube for passing a guidewire insidethereof is arranged so as to pass inside the balloon and the balloon andthe small-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein aflexural modulus of elasticity of the material constituting at leastthat part of the small-diameter portion on the distal end side in saidtube which is fused to the balloon is less than the flexural modulus ofelasticity of the material constituting the balloon, wherein a ratio ofthe outer diameter of the small-diameter portion on the distal end sidein said tube to the outer diameter of the proximal end portion, (outerdiameter of the small-diameter portion on the distal end side)/(outerdiameter of the proximal end portion), is no less than 0.85, wherein theouter diameter of the small-diameter portion on the distal end side insaid tube is no more than 0.52 mm, wherein a proximal end of an X rayimpermeable ring is abutted against and permanently fixed to theboundary portion of the proximal end side and the small-diameter portionon the distal end side of the tube for passing a guidewire insidethereof, wherein a tube constituting the outer surface of the catheteris composed of a material that can be fused with the balloon and isfused and arranged on the proximal end side of the balloon.
 4. A medicalballoon catheter composed of a plurality of tubes and a balloon, thiscatheter having a structure in which a tube formed to have an outerdiameter on a distal end side is consistently smaller along the entirelength thereof than that on a proximal end side and serving as a tubefor passing a guidewire inside thereof is arranged so as to pass insidethe balloon and the balloon and the small-diameter portion on the distalend side in said tube are fused together in the vicinity of the distalend of the catheter, wherein a melting point of the materialconstituting at least that part of the small-diameter portion on thedistal end side in said tube which is fused to the balloon is lower thanthe melting point of elasticity of the material constituting theballoon, wherein a ratio of the outer diameter of the small-diameterportion on the distal end side in said tube to the outer diameter of theproximal end portion, (outer diameter of the small-diameter portion onthe distal end side)/(outer diameter of the proximal end portion), is noless than 0.85, wherein the outer diameter of the small-diameter portionon the distal end side in said tube is no more than 0.52 mm, wherein aproximal end of an X ray impermeable ring is abutted against andpermanently fixed to the boundary portion of the proximal end side andthe small-diameter portion on the distal end side of a tube for passinga guidewire inside thereof, wherein the tube constituting the outersurface of the catheter is composed of a material that can be fused withthe balloon and is fused and arranged on the proximal end side of theballoon.
 5. A medical balloon catheter composed of a plurality of tubesand a balloon, this catheter having a structure in which a tube formedto have an outer diameter on a distal end side is consistently smalleralong the entire length thereof than that on a proximal end side andserving as a tube for passing a guidewire inside thereof is arranged soas to pass inside the balloon and the balloon and the small-diameterportion on the distal end side in said tube are fused together in thevicinity of the distal end of the catheter, wherein a part of thesmall-diameter portion on the distal end side in said tube which isfused to the balloon is composed of a polyester elastomer having hardsegments and soft segments in a molecule and a ratio of the softsegments is higher than 13%, wherein a ratio of the outer diameter ofthe small-diameter portion on the distal end side in said tube to theouter diameter of the proximal end portion, (outer diameter of thesmall-diameter portion on the distal end side)/(outer diameter of theproximal end portion), is no less than 0.85, wherein the outer diameterof the small-diameter portion on the distal end side in said tube is nomore than 0.52 mm, wherein a proximal end of an X ray impermeable ringis abutted against and permanently fixed to the boundary portion of theproximal end side and the small-diameter portion on the distal end sideof a tube for passing a guidewire inside thereof, wherein the tubeconstituting the outer surface of the catheter is composed of a materialthat can be fused with the balloon and is fused and arranged on theproximal end side of the balloon.
 6. A medical balloon catheter composedof a plurality of tubes and a balloon, this catheter having a structurein which a tube formed to have an outer diameter on a distal end side isconsistently smaller along the entire length thereof than that on aproximal end side and serving as a tube for passing a guidewire insidethereof is arranged so as to pass inside the balloon and the balloon andthe small-diameter portion on the distal end side in said tube are fusedtogether in the vicinity of the distal end of the catheter, wherein apart of the small-diameter portion on the distal end side in said tubewhich is fused to the balloon is composed of a polyamide elastomerhaving hard segments and soft segments in a molecule and a ratio of thesoft segments is higher than 14%, wherein a ratio of the outer diameterof the small-diameter portion on the distal end side in said tube to theouter diameter of the proximal end portion, (outer diameter of thesmall-diameter portion on the distal end side)/(outer diameter of theproximal end portion), is no less than 0.85, wherein the outer diameterof the small-diameter portion on the distal end side in said tube is nomore than 0.52 mm, wherein a proximal end of an X ray impermeable ringis abutted against and permanently fixed to the boundary portion of theproximal end side and the small-diameter portion on the distal end sideof a tube for passing a guidewire inside thereof, wherein the tubeconstituting the outer surface of the catheter is composed of a materialthat can be fused with the balloon and is fused and arranged on theproximal end side of the balloon.